This application is a continuation of copending French application FR 01.03177, filed Mar. 8, 2001. The priority of this application is claimed herein, and the entire disclosure of this application is incorporated herein by reference.
1. Technical Field
The invention relates to the field of valves used in plant involving the distribution of fluids. It finds a particular application especially in chemical plants which mix various products, such as is the case, for example, in the lubricant industry, the paint industry, or in papermaking plant. It relates more specifically to a directional-control valve which allows two pipes to be connected, and which at the same time has sealing properties while being compatible with cleaning by passing a scraper through.
2. Prior Art
In general, plant involving the distribution of liquid products comprises several pipes or lines inside which the product or products distributed flow. Depending on the various destinations of the products, it may be necessary to connect certain pipes with certain others using valves. The directional-control valves therefore allow a first pipe to be connected to a second.
Thus, in general, these valves are intended to connect a first pipe known as a xe2x80x9cmain pipexe2x80x9d to a second pipe known as a xe2x80x9csecondary pipexe2x80x9d which is generally at right angles to it. Where the main pipe and the secondary pipe meet, the valve has a moving member which, depending on the position it occupies, either connects or does not connect the main pipe and the secondary pipe. An example of a valve such as this is described in document U.S. Pat. No. 3,068,901.
When the plant conveys different products, it may be important to guard against the risk of contamination of one product with traces of a product which passed down a pipe previously. This is why certain pipes need to be cleaned after a first fluid has passed. To facilitate these cleaning operations, and in particular to automate them, it is known practice to use scrapers which are elements which have an outside diameter roughly equal to the inside diameter of the pipes in which they run. These scrapers, as they move, carry along the traces of the liquid or fluid which remain in the pipe. An example of the use of a scraper in a valve is given in document U.S. Pat. No. 3,063,079.
A first problem that the invention sets out to solve is therefore that of providing a valve which is compatible with the passage of a cleaning scraper.
In order to place various pipes in communication using directional-control valves, several solutions have already been proposed.
Thus, one known solution involves plug valves in which the moving member situated in the valve is able to move at right angles to the main pipe. This moving member has a portion forming a through-orifice which has a diameter identical to that of the main pipe. Thus, a scraper running down the main pipe can pass through this orifice. When the moving member is moved, it occupies a position in which it is situated partly in the middle of the main pipe, thus opening the passage between the main pipe and the secondary pipe. This kind of valve therefore has the advantage of preventing the scraper from running through when the valve is open, that is to say when fluid can circulate from the main pipe to the secondary pipe.
By contrast, this type of valve has the major disadvantage of not providing sealing between the upstream port and the downstream port of the main pipe when the valve is open.
A first problem that the invention sets out to solve is that of providing sealing between the upstream port and the downstream port of the main pipe when the valve is open.
Another known type of directional-control valve is the valve commonly known as a ball valve. In this kind of valve, the moving member is a sphere, which is pierced with a through-orifice intended to place the ports of the valve on each side of this orifice in communication. Examples of this type of valve are described in documents U.S. Pat. No. 5,113,895 and EP 0 563 853.
Such a valve has the major disadvantage of being mechanically complex, because it entails precise machining of the spherical moving element, which greatly increases the cost price of such a valve.
There are also known other directional-control valves generally known as butterfly valves, such as the one described in particular in document U.S. Pat. No. 5,193,572. The moving member of such a valve shuts off the passage between the main pipe and the secondary pipe. As it moves, the moving member partially enters the main pipe, and in this position forms an obstacle to the scraper, thus preventing the latter from traveling unintendedly into the plant. This type of valve also has the major disadvantage of maintaining a connection between the upstream port and the downstream port of the main pipe in both positions of the moving member.
The objective of the invention is to provide a valve which allows a scraper to pass along the main pipe, while at the same time providing optimum sealing between the main pipe and the secondary pipe when necessary, or alternatively sealing between the upstream port and the downstream port of the main pipe.
The invention therefore relates to a directional-control valve intended to connect a first pipe known as a main pipe and a second pipe known as a secondary pipe. This valve comprises, in the known way, an upstream port and a downstream port which are connected to the main pipe and have identical diameters, and a third connection port connected to the secondary pipe.
This valve also comprises a shut-off member capable of moving at right angles to the main pipe, between two positions, namely:
a first position, known as a closed position, in which the shut-off member has a first orifice, of a diameter identical to that of the upstream port and downstream port, positioned in line with said upstream port and downstream port, so as to allow fluid to pass through the main pipe;
a second position known as the open position, in which the shut-off member has a second orifice opening, on the one hand, toward the upstream port and, on the other hand, toward the third connection port, so as to place the upstream port and the secondary pipe in communication.
According to the invention, this valve is one wherein the diameter of the upstream port and the downstream port is chosen to allow a scraper to pass, and the second orifice of the shut-off member has means for preventing the scraper, coming from the upstream port, from entering the second orifice of the shut-off member.
In other words, the shut-off member has a through-orifice, the inside diameter of which corresponds to that of the main pipe. When this through-orifice faces the upstream port and the downstream port, the continuity of the main pipe is ensured with a constant diameter over the entire passage through the valve. The scraper can therefore pass, and this scraper can act effectively along the entire length of the main pipe, particularly in the region of the valve.
When the shut-off member moves, the communication between the downstream port and the secondary pipe is cut off, and the communication between the upstream port and the secondary pipe is established, and this allows the fluid to flow from the main pipe into the secondary pipe. In this configuration, the scraper is stopped in its progression inside the upstream port so that it does not impede the movement of the shut-off member when the valve switches from the open position to the closed position.
Advantageously in practice, the valve comprises sealing means arranged both between the upstream port and the shut-off member, and between the downstream port and the shut-off member. These sealing means provide sealing between the primary and secondary pipes in both positions of the shut-off member.
In other words, when the valve is closed, sealing between the main pipe and the secondary pipe is provided so that no fluid can pass from the main pipe to the secondary pipe. When the valve is in the open position, sealing is provided between the downstream port and the upstream port and the third connection port connected to it. Thus, fluid coming from the main pipe from the upstream port is routed in its entirety into the secondary pipe without any risk of it continuing on its way in the main pipe via the downstream port.
Advantageously in practice, the shut-off member has two flat faces in these regions facing the upstream port and the downstream port. Thus, the sealing means arranged between the upstream port and the downstream port, and the shut-off member are of planar geometry, therefore of conventional design. They are also easier to arrange.
In a preferred embodiment, these sealing means may consist of O-rings, the centers of which lie on the axis of the main port.
Advantageously in practice, the valve according to the invention may comprise at least one rinsing nozzle located in the third connection port and able to shower the region where the third port and the main pipe meet. Thus, it is possible to clean the region of the valve which is not accessible to the scraper, and it is possible in this way to avoid any risk of contamination or pollution of successive products passed through the characteristic valve.
In a preferred embodiment, one of these rinsing nozzles may be directed into the position that the scraper occupies when the latter comes into contact with the means preventing it from entering the second orifice of the shut-off member. Thus, it becomes possible to clean not only the body of the valve and the shut-off member, but also the scraper which comes into contact with this shut-off member when the valve is open.
In practice, the shut-off member may be moved by a great many actuators isolated from the body of the valve such as, for example, manual actuators or pneumatic rams or alternatively electrical devices.